Device for diaphragming x-rays



March 28, 1950 Filed May 9, 1946 D. E. BERGGREN 2,501,756

DEVICE FOR DIAPHRAGMING X-RAYS 2 Sheets-Sheet 1 INVENTOR ATTORNEY March28, 1950 E. BERGGREN 2,501,756

DEVICE FOR DIAPHRAGMING X-RAYS Filed May 9, 1946 2 Sheets-Sheet 2INVENTOR 574 0F 5 MAM/f L BERGGRf/V Patented Mar. 28, 1950 UNITED STATESPATENT OFFICE DEVICE FOR DIAPHRAGMING X-RAYS Application May 9, 1946,Serial No. 668,377 In the Netherlands March 21, 1942 Section 1, PublicLaw 690, August 8, 1946 Patent expires March 21, 1962 Claims. (Cl.250-105) In screening by means of X-rays it is usual to stop the beam ofX-rays to such a degree as is admissible in view of the range to beviewed. This is essentially effected for reducing the detrimentalsecondary radiation.

In order to explore a body to be examined by means of the diaphragmedbeam the X-ray tube and the fluorescent screen are usually coupled andjointly movable in a vertical and horizontal direction, the X-ray tubebeing so placed that the centre of the beam of rays transmitted by thestop coincides with the centre of the screen.

The device for stopping the rays usually consists of a housing which isshaped as a flat box having a window and is secured to the X-ray tube.This housing contains the stop proper which is made from a material bywhich the X- rays are strongly absorbed. As a rule use is made of a beamhaving arectangular section, and the size and ratio of the lengths ofthe sides of this section are variable. In this case the housing has asquare window and the stop is constituted by two pairs of coupledslides, one pair being movable in a vertical direction and the otherpair in a horizontal direction symmetrically with respect to the centerlines of the square'window.

The movable system consisting of.the X-ray tube and the fluorescentscreen represents a considerable mass; although it is balanced out bycounterweights or by springs the continuous displacement of this mass inscreening requires much bodily exertion in the long run. Hence, aprogress is achieved if the device for stopping the rays is so arrangedas to be movable with respect to the X-ray tube, so that the centre ofthe aperture of the stop can be shifted in every direction of its plane.In this case an optional part of the beam of rays emitted by the X-raytube can be admitted to the fluorescent screen and in screening thewhole object can be explored by moving solely the housing and the stopcontained therein in front of the X-ray tube. The X-ray tube itself andthe fluorescent screen need no longer be shifted.

The invention envisages another simplification. According to theinvention, in a device for stopping X-rays, in which a stop is lodged ina housing having a window for the passage of the rays, the stop ismovable with respect to the housing in such manner that the centre ofthe aperture is movable relatively to the centre of the window. By meansof the device according to the invention the stopped beam of X-rays canbe moved over the fluorescent screen without the need of shifting theX-ray tube or the housing of the stop.

The invention may be used both with a stop, having an invariableaperture and with a stop having a variable aperture, for instance a stopconsisting of two dovetailed plates of an iris s op.

The stop is preferably movable to such a degree that with the smallestaperture to be adjusted the edge of the aperture can still be brought tothe edge of the window which permits a maximum field to be covered,irrespective of the fact how far the stop is opened. The larger theaperture the smaller the required deflection.

According to the invention, a device for obtaining a rectangular sectionof the beam of rays, which comprises a stop operating with the usualfour closing plates each of which bounds one side of the section of thebeam, comprises a mechanism for moving the closing plates with respectto the housing, by means of which each pair of opposite sides of therectangle can be moved at will in opposite directions symmetrically orin the same direction with a constant distance. The control of such adevice can be simpler than that of a device in which the housing followsthe movement of the stop. In the last-mentioned device sepa rate knobsare required for choosing the size and the place of the aperture withrespect to the X- ray tube, since in one case solely the closing platesare to be shifted, and in the other case motive power has to be exertedon the housing. In the device according to the invention the same partsmust be shifted in both cases and a similar movement is wanted. Thispermits the control knobs for the two adjustments to be easily combined.

This may be effected by connecting the closing plates mechanically to amovable element which can be shifted by means of a control knob. Thiselement should be movable along a line and, moreover, be rotatable aboutan axis cutting this line. One movement of the closing plates can thenbe performed by the linear displacement and the other movement byrotation of the movable element.

This will be more fully explained by reference to Figures 1, 2 and 3 ofthe drawing.

Figures 1 and 2 represent very schematically two examples of theactuating mechanism on only one pair of closing plates and in Fig. 3,which is another example thereof, both pairs are also represented veryschematically.

The two closing plates bounding the horizontal sides of the rectangularsection of the beam are constructed to constitute flat slides designatedby l and 2 in Fig. 1. One may imagine the upper slide I to be suspended,by means of a rod 3, from.

one end of a lever 4 whose other end can be moved up and down by meansof a rod 5. This rod is shifted in its turn by means of a yoke 6 whichis to be considered as the above-mentioned movable element. At theopposite end of the yoke the bottom slide 2 is suspended by means of therod 1. The middle of the yoke 6 is movable in a vertical slot 8. Thismiddle portion has also secured to it the handle 9. By means of thishandle the yoke can be lifted along the line III untilit occupies theposition indicated by the line i I, the rod 4 pivoting about the pointI2 and the side I descending, the slide 2 being at the same time liftedby the rod I. Consequently, the plates -I and 2 approach each other, theslit indicated by a becomes steadily narrower, but the centre of theslit remains at the same point. Finally the slit is completely closed.

The handle 9 may also be turned about an axis normal to the line I!)through the point I3. In this case the yoke 6 occupies the positionindicated by the line l4. During this displacement the left-hand end ofthe lever 4 descends and the slide I rises, the slide 2 rising too.Consequently the distance between the opposite sides of the rectangularsection of the beam bounded by the plates I and 2 remains constant, butthe slit moves from a to b.

In this way the handle 9 permits the vertical width of the slit to .bevaried, but also the slit to be moved .over the fluorescent screen in avertical direction.

The device may also be such that by moving the yoke along the line II)the slit is shifted and by rotation of the yoke about the point l3 the 7width of the slit is varied. This is illustrated in Fig. 2. Both of theplates are suspended from the yoke by a rod the plate I by the rod is.at the right hand end and the plate .2 by .therod I5 .at theleft-handend.

A similar mechanism may be used for the plates bounding the verticalsides of the rectangle. In this way the four movements can beaccomplished by means of two control knobs. Instead of the closingplates being actuated by means of levers and rods this may be effectedby a system of Bowden wires. Such a system is schematically representedin Fig. 3, where the reference number 2| designates the housing of thestop whose front plate has a square window 22. The closing plates 23 and24 bound the 'vertical sides of the rectangular section of the beam of'X rays passing through the window 22, whereas two other closing plates25, 26 bound the horinarrower as the wires 21 and 28 are slackened.

In the same way the plates 25 and 26 are movable in a verticaldirection. by means of Bowden wires 3! and 32.

The end of the wires 21 and 28 is connected to a slidable and rotatableyoke 33, whereas the end of the wires 3| and 32 is connected toa-slidable and rotatable yoke 34. When lifting the yoke 34 both of thewires 3| and 32 are slackened and the slit between the plates 25 and 26becomes narrower. When lifting the yoke '33 the slit between the plates23 and 24 becomes narrower.

The yoke 34 has been represented in a horizontal position and the yoke33 in an oblique position, because the slit has been shifted to theleft-hand side of the window 22. When turning the yoke i and islaterally supported therein.

4 33 about the axis 35 in a clock-wise direction the wire 28 is pulledand at the same time the wire 21 is slackened. Consequently the slides23 and 24 move simultaneously with a constant relative distance over thewindow 22 to the right and upon further rotation of the yoke theaperture 36 of the stop moves to the extreme position at the oppositeside of the window 22. Similarly a displacement of this aperture in avertical direc- .tion can be obtained by rotation of the yoke 34 abouttheaxis 31.

.An accurate adjustment of the vertical and horizontal width of the slitcan be obtained by a helicoidal movement. To this end the controlknob,'in another form of construction of the device according to theinvention, is secured to a screw spindle which is movable about its axisby means of this knob. Moreover, the screw spindle is'movable about anaxis cutting the axis of the spindle. It carries a nut which uponrotation of the spindle about its axis does not follow this movement andmay be connected to the closing plates by means of Bowden wirestransmitting its movement-to these plates. In this construction the nutconstitutes the movable element which by turning the screw is movedalong-the axis of the screw spindle and, moreover, can be turned aboutan axis cutting the spindle. 1

The actuating mechanism of the stop according to the invention can befurther simplified by uniting the control knob of one pair of clos-' ingplates and that of the other pair to form an assembly. By-moving themovable element associated with one pair of plates along a line and bymoving the movable element associated with the other pair of platesalong the same line one obtains one movement of the closing plates, forinstance, the opening and closing of the slit; By rotation of thecombined control knobs about two axes cutting each other at right anglesat a point of the'said line the other movement of the closing plates isobtainable -i. e. shifting'of the slit in the present example. In thiscase two co-axial screw spindlesmay be used, one of which projects fromthe other and each comprising a control knob and a nut supported on ayoke which is rotatable about the point of intersection of a stationaryshaft and the common axis of the screwspindles bymeans of a cardan jointor a ball and 'socket'joint. To both of the nuts are secured Bowdenwires by which the movement '01 the nuts is transmitted to the closingplates of the stop. The shafts of these Bowden wires are secured withtheir ends crosswise around the stationary shaft and end parallel withthis shaft.

One'form of construction of this device is rep resented in Fig. 4. Ascrew spindle M is rotatable in a-tube42 and restsin a step bearing 43,the tube 42 being also provided with screw thread at the .outside. Thestep bearing 43 is secured to a'yoke'44. In order to support the coaxialscrew spindles M and 42 a plate 45 and a cup 46 are secured to the yoke44. The spindle 42 passes to the outside through an aperture in thiscu'pBelow the yoke is a cardan joint 41 constituting a coupling between ashaft 49, which is stationary with respect to a bed plate 48 and extendsnormally to this plate, and-the movable axis 52 of the screw spindles.The screw spindle 4i carries a nut 50. To the end of the spindle 4|which stands above the spindle-His secured a control knob 5|. On'turning this knobthe .spindle 4 I rotates about its axis-and the nutmoves along the axis 62.

The spindle -42 also carries a nut, which is designated by 53, and acontrol knob 54. On turning the knob 54 the nut 53 waves along the shaft52. The nuts and 53 are prevented from following this movement by rods55 and 56 which slide between two partitions 57 secured to thecup 45.Upon displacement of the movable elements 50 and 53 along the line 52the yoke does not follow this movement in this case, but the Bowdenwires 58 and 59, whose ends are secured to the nut 50, and the Bowdenwires 56 and GI (indicated in dotted lines) which extend in a planenormal to the plane of the drawing and whose ends are secured to the nut53, are pulled on turning the knobs 5| and 54 if the nuts are moved awayfrom the yoke 44 and slackened if they are moved towards the yoke. Theypass over a spherical part of the yoke 44 and through radial slits 62 inthe plate 45.

The shafts 63 of the Bowden wires end parallel with the stationary shaft49 and are secured crosswise about this shaft in apertures oi the bedplate 48. They are jointly surrounded by a funnel 64 which is secured tothe bed plate and emerges into a tube 55 which may be flexible so thatit can be easily placed along the constructional parts of the screeningstand.

The other end of the wires 55 and 59 may be imagined to be secured tothe closing plates bounding the vertical sides of the section of thebeam of X-rays, whereas the other end ofthe wires and 6| is secured tothe two other closing plates.

If on turning the knob 5| the nut 55 is moved away from the yoke 44 thewires 58 and 59 are pulled over the same distance. Consequently the jawsof the closing plates, to which these wires are secured, for instancethe plates 23 and 24, move away from each other, one of them passing asfar to the left as the other moves to the right. Consequently the slitbetween the plates becomes broader but the centre of the slit remains atthe same point. The same holds for the two other plates if by turningthe knob 54 the nut 53 is moved away from the yoke 44'. When moving thenut in an opposite direction along the shaft 52 the springs 29 and 30(Fig. 3) keep the wires taut and cause the jaws of the closing plates toapproach each other so that the slit becomes narrower without the centreof the slit being shifted. Hence, the size and the ratio of the sides ofthe image field can be controlled by means of both control knobs 5| and54 jointly constituting one handle.

The spindles ll and 42 are also rotatable about an axis 55 (normal tothe plane of drawing), by which the axis 52 is normally cut, and aboutan axis Bl normally cutting the axis 65 at the same point as the axis52. The cup 45 is shaped as a hemisphere whose centre is located in thepoint of intersection of the three axes 52, 66 and 61. It is partlysurrounded by a dust helmet 68 having a spherical portion which adjoinsa cylindrical portion secured to the bed plate 43.

When turning the spindle 41 about the axis 56 so that the axis isshift-ed from 52 to 59, the wire 58 is slackened, whereas the wire 59 ispulled.

In this case both of the jaws of the closing plates 23 and 24 move inthe same direction and their relative distance remains the same. Thecentre of the slit is now shifted over the image field but the width ofthe slit remains unchanged. The two other plates do not move, since thewires 6|] and 5| bend themselves about the edge of the slits 62 in theplate 45 but do not move in their own direction.

When it is desired to raise or lower the slit this may be efiected byturning the spindle 42 about the axis 51. In this case the wires 58 and59 are not shifted, but bend themselves only about the edge of the slots62, which are visible in the drawing, whereas the wires 50 and 6|provide for a displacement of the plates 25 and 25 in the samedirection. The four movements referredto may be combined, thus bringingthe centre of the aperture of the stop at any point of the image.

field, and the aperture can be made as high and as bright as is allowedby the slide construction in the housing 2|.

Since a rotation in a clockwise direction usually corresponds to aclosing movement that is good practice to provide the spindles 4i and 42with a left-handed screw thread. When turning the knobs 5| and 54 in aclockwise direction the nuts 50 and 53 move towards the yoke 44 and thewires are slackened, so that the slits are closed.

Of course, the same can also be achieved with a right-handedscrew-thread if the movement at the stop is reversed by a lever systemor toothed gearing. In this case the springs have to separatethe'closing plates. Such a reversing system may also be used forincreasing or decreasing the displacement of the plates.

Easy control is also promoted by providing that the upward movement ofthe knobs 5| and 54 corresponds to the rise of the aperture 35, and themovement of these knobs to the left corresponds to a lateraldisplacement of this aperture to the left. This may be considered insecuring the operating mechanism (shown in Fig. 4) to the stand. In thiscase, the exploration of the image field and adjustment of the apertureof the stop is extremely simple. What I claim is: 1. X-ray apparatuscomprising an X-ray tube housing, a window in said housing, a diaphragmthe beam, and a common control mechanism for simultaneouslyactuatingeach pair of shutters selectively to move in opposite and thesame directions an equal distance for altering the dimensions of saidaperture and to move the center of said aperture relative to the centerof said Window.

2. X-ray apparatus comprising an X-ray tube housing, a window in saidhousing, a diaphragm for defining an effective aperture in said Windowof said housing for the passage of a beam of X- rays comprising twopairs of adjustable shutters impervious to X-rays for defining a sectionof ters selectively to move in opposite and in the same directions anequal distance for altering the dimensions of said aperture and to movethe center of said aperture relative to the center of said window, andflexible members coupling said control member to said shutter totransmit movement of said control member to produce movement of saidshutters.

3. X-ray apparatus comprising an X-ray tube housing, a window in saidhousing, a diaphragm for defining an effective aperture in said windowof said housing for the passage of a beam of X- rays comprising aplurality of adjustable shutters impervious to X-rays, a control membermovable along an axis to efiect movement of said shutters in order thatthe center said aperture is moved relative to the center of said windowand rotatable about'an axis perpendicular to said axis of movement toeffect movement of said shutters in order that the dimensions of saidapertures are altered, and flexible members coupling said control memberto said shutters to transmit movements of said control element toproduce the corresponding movements of said shutters.

4. X-ray apparatus comprising an X-ray tube housing, a window in saidhousing, a diaphragm for defining a rectangular aperture in said windowof said housing for the passage of a beam of X-rays from said tubecomprising four adjutable shutters impervious to X-rays, a first controlmember movable along an axis to efiect lateral movement of one; pair ofsaid shutters and rotatable about an axis perpendicular to said axis ofmovement to effect movement of said pair of shutters toalter the, onedimension of said rectangular aperture, a second control member movablealong a second axis to effect lateral movement of a second pair ofshutters and rotatable about an axis perpendicular to said second axisof movement to effect movement of said second pair of shutters to alterthe other dimensions of said rectangular aperture, and flexible memberscoupling said control members to said respective pairs of shutters toproduce the corresponding movements of said shutters.

5. X-ray apparatus comprising an X-ray tube housing, a window in saidhousing, a diaphragm in said housing for defining a rectangular aperturein said window of saidhousing for the passage of a beam of X-rays fromsaid tube com prising four adjustable shutters impervious to xrays, anda control mechanism for adjustably positioning said shutters withrespect to said window to alter the dimensions of said rectangularaperture and to move the center of said aperture relative to the centerof said window comprising a pair of coaxial screw spindles, a nut oneach spindle movable laterally along said spindle when said spindle isrotated, a shaft member, means to rotate said coaxial spindles aboutsaid shaft member, and flexible members coupling each of said nuts torespective pairs of shutters to transmit lateral movement of said nut toactuate each pair of shutters to move in opposite directions an equaldistance to alter the dimensions of said aperture and to transmit rotarymovement 01' said spindles about said shaft member to actuate each pairof shutters to move in the same direction an equal distance to move thecenter of said aperture relative to the center of said window.

DETLOF EMANUEL BERGGREN.

REFERENCES CITED The iollowing references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,117,266 Snook et a1. Nov. 17,1914 1,709,626 McGunnigle Apr. 16, 1929 1,738,945 Brenkert et a1. Dec.10, 1929 1,909,118 Raab May 16, 1933 1,953,497 Nelson Apr. 3, 19342,082,965 Lundquist June 8, 1937

